Itchy Armpits! Help!!!

I'm 16 weeks going on 17th. Since about 1 week ago, I developed rashes on my armpits! These are red bumps. Itch so bad whenever I perspire and especially at night! Now the side of my breasts, back of my knee and elbows have rashes too. I've gone to the GP and he prescribed me with Xyzal pills and Dermasone cream but they don't seem to help. Any alternative?